The art relating to small electric lamp bulb sockets and bulb mounting assemblies long has recognized certain requisite design parameters such as the need to accommodate easy bulb replacement and the desirability of minimizing the number of assembly parts. This latter consideration contributes greatly to minimizing the total cost of manufacture of what commonly is a high volume production product. It has proven complex to obtain these design goals in the case of bulb mounting assemblies that are subjected to corrosive atmospheres and excessive vibrations, such as assemblies used on the exteriors of vehicles as running lights, while maintaining reliability of function for both the mounting assembly and the lamp bulb mounted therein.
One expedient that is known in the art is the formation of the mounting assembly housing as a one-piece molding from electrically insulating material such as rubber or flexible plastic. Examples of this are disclosed by U.S. Pat. No. 2,099,405 issued Nov. 16, 1937, U.S. Pat. No. 2,741,747, issued Apr. 10, 1956, and U.S. Pat. No. 3,182,279, issued May 4, 1965. Assembly housings as taught by these patents reduce the number and complexity of assembly parts. Also, in the case of U.S. Pat. Nos. 2,099,405 and 3,182,279, the resiliency of the housing material is exploited to eliminate the need for a spring part often used to bias an electrical lead into current transmitting contact with the terminal at the extremity of the bulb base.
Use of devices as taught by these patents on the exterior of vehicles and in like environments does pose, however, certain potential difficulties. While the prior art molded housings greatly reduce the transmission of vibrations through the mounting assemblies to the bulb as compared to assemblies having metal housings, substantial metal to metal contact between parts functioning as electrical leads and the bulb base still serves to transmit deleterious vibrations to the bulb filament which shorten the useful life of the bulb. Such substantial metal to metal contact and the proximity of metal to the bulb base also give rise to the distinct possibility of oxidation in the corrosive atmosphere of vehicle usage, making removal of the bulb difficult or impossible at the time bulb replacement is necessary.
Additionally, in order that the materials of the prior art molded housings be sufficiently resilient to provide the desired biasing force between an electrical lead and the bulb base terminal such materials commonly are relatively soft and flexible elastomers. Because of their softness and flexibility, such materials have a tendency to wear at interfaces with vehicle mounting structure because of vibrations and offer little protection to the enclosed bulb in the event the assembly housings are impacted by stones, gravel or because of slight collisions with structures such as fences, walls or other vehicles. Such collisions often may happen since running lights commonly are positioned at the exterior limits of vehicles.
It is, therefore, an object of this invention to provide an electric lamp mounting assembly that includes a one piece housing of insulating material in order to minimize the number of assembly parts and provide for ease and economy of manufacture. A further object of the invention is to provide a mounting assembly of a design that minimizes to the greatest extent possible metal to metal contact involving the mounted bulb to reduce the chances of corrosion involving and proximate the bulb. A still further object is to insulate the bulb to a large extent from vibrations occurring in surrounding structure to which the assembly is attached. Additionally, it is an object of the invention to eliminate the need for a spring part urging an electrical lead into contact with the bulb terminal by utilizing a biasing force provided by the resilient deformation of the housing material itself, while still using a semi-rigid, wear and impact resistant housing material. All of these objects are provided while retaining a simple and easily accomplished bulb mounting and removal arrangement together with reliability of electrical functioning for the assembly parts.